The U.S. Postal Service (U.S.P.S.) has adopted a numeric code, the well known zip code, for the identification of post offices and distribution centers. In order to permit mechanization of a previously labor-bound operation of sorting the mail, the U.S.P.S. has also adopted a binary bar - half bar code which can be printed on each letter, which can be electronically scanned, and which enables rapid sorting into appropriate bins. (See Postal Service Notice 23E, October 1972 "Guidelines for Designing and Printing Envelopes for Machine Processing.")
At present the U.S.P.S. applies the five digit zip code only to business reply envelopes and cards. This code, which is divided into two sections or groups of numbers, respectively comprising the first three numbers and the last two numbers, is encoded using straight binary code. For example, the zip code 15034 has a first section of 150 and a second section of 34. The number 150 in binary is 0010010110, using a ten bit representation, and the number 34 is represented by seven binary bits 0100010. The corresponding bar - half bar code for 150 is and for 34 is. Since straight binary and not a binary coded decimal is used, console encoding requires a computer capable of decimal to binary conversion and the sorting machines used require sophisticated logic circuitry to decode the characters.